1. Field of the Invention
Example embodiments of the present invention relate to a joint pattern beam sectorization method and apparatuses performing the same.
2. Description of the Related Art
Massive multiple-input and multiple-output (MIMO) communication technology may be wireless transmission technology using a large number of antennas in a base station or a repeater. In the massive MIMO communication technology, interference between user equipment (UE) signals may be spatially controlled through the same beamforming. Thus, the large number of UEs may be simultaneously served using the same amount of wireless resources, and power consumption per UE may be reduced by an inverse number of the number of antennas.
Based on the above technology, the beamforming may be applied for each of the UEs in a wide service target region, for example, three sectors in general. In this example, to implement the technology based on a frequency division duplex (FDD) scheme, massive MIMO channel state information (CSI) may be estimated in the UE and transmitted to a base station as a feedback such that the base station determines a beamforming weight based on the massive MIMO CSI. For this reason, such a large amount of feedback may be an issue to be solved to implement the technology. When the number of massive antennas is M, and when the number of UEs having a single antenna is K, M*K CSI feedbacks may be used in typical sectorization technology. Here, M is an integer greater than K.
To solve the issue, a sector of the typical 3-sector system may be divided into a plurality of beam sectors, and beam division multiple access (BDMA) technology and joint space division and multiplexing (JSDM) technology may be suggested as typical MU-MIMO communication technology in the beam sector.
When the number of beam sectors is B, beamforming of the massive MIMO communication system may be performed using B×(K/B*K/B)=(K/B)*K CSI feedbacks based on the BDMA technology and the JSDM technology. Thus, an amount of CSI feedbacks may be reduced by M/(K/B) times when compared to the typical system.
The BDMA technology and the JSDM technology may be effectively used to reduce the amount of CSI feedbacks by dividing an entire service target region into beam sectors.
A massive antenna array may occupy a large space to implement the BDMA technology and the JSDM technology in a cellular band. For example, at least an area corresponding to a value of Nr*Nc*(λ/2)2 may be used to implement a multiple beam sector or multiple beam employing the massive antenna array as a planar array having Nr*Nc elements. Also, planar arrays corresponding to the number of MIMO transmission antennas may be necessary to apply the MIMO communication technology for each of the beam sectors.